Nozzle for bladeless fan assembly with heater

ABSTRACT

A bladeless fan assembly for creating an air current includes a nozzle mounted on a base housing a device for creating an air flow. The nozzle includes an interior passage for receiving the air flow and a mouth for emitting the air flow. The nozzle defines, and extends about, an opening through which air from outside the fan assembly is drawn by the air flow emitted from the mouth. The nozzle also includes a heater for heating the air flow upstream of the mouth.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/222,167, filed Mar. 21, 2014, which is a continuation of U.S. patentapplication Ser. No. 13/481,268, filed May 25, 2012, now U.S. Pat. No.8,714,937, which is a continuation of U.S. patent application Ser. No.12/716,780, filed Mar. 3, 2010, now U.S. Pat. No. 8,197,226, whichclaims the priority of United Kingdom Application Nos. 0903682.3, filedMar. 4, 2009, and 0911178.2, filed Jun. 29, 2009, the entire contents ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a fan assembly. In a preferredembodiment, the present invention relates to a domestic fan, such as atower fan, for creating a warm air current in a room, office or otherdomestic environment.

BACKGROUND OF THE INVENTION

A conventional domestic fan typically includes a set of blades or vanesmounted for rotation about an axis, and drive apparatus for rotating theset of blades to generate an air flow. The movement and circulation ofthe air flow creates a ‘wind chill’ or breeze and, as a result, the userexperiences a cooling effect as heat is dissipated through convectionand evaporation.

Such fans are available in a variety of sizes and shapes. For example, aceiling fan can be at least 1 m in diameter, and is usually mounted in asuspended manner from the ceiling to provide a downward flow of air tocool a room. On the other hand, desk fans are often around 30 cm indiameter, and are usually free standing and portable. Floor-standingtower fans generally comprise an elongate, vertically extending casingaround 1 m high and housing one or more sets of rotary blades forgenerating an air flow. An oscillating mechanism may be employed torotate the outlet from the tower fan so that the air flow is swept overa wide area of a room.

Fan heaters generally comprise a number of heating elements locatedeither behind or in front of the rotary blades to enable a user tooptionally heat the air flow generated by the rotating blades. Theheating elements are commonly in the form of heat radiating coils orfins. A variable thermostat, or a number of predetermined output powersettings, is usually provided to enable a user to control thetemperature of the air flow emitted from the fan heater.

A disadvantage of this type of arrangement is that the air flow producedby the rotating blades of the fan heater is generally not uniform. Thisis due to variations across the blade surface or across the outwardfacing surface of the fan heater. The extent of these variations canvary from product to product and even from one individual fan heater toanother. These variations result in the generation of a turbulent, or‘choppy’, air flow which can be felt as a series of pulses of air andwhich can be uncomfortable for a user. A further disadvantage resultingfrom the turbulence of the air flow is that the heating effect of thefan heater can diminish rapidly with distance.

In a domestic environment it is desirable for appliances to be as smalland compact as possible due to space restrictions. It is undesirable forparts of the appliance to project outwardly, or for a user to be able totouch any moving parts, such as the blades. Fan heaters tend to housethe blades and the heat radiating coils within a moulded aperturedcasing to prevent user injury from contact with either the moving bladesor the hot heat radiating coils, but such enclosed parts can bedifficult to clean. Consequently, an amount of dust or other detrituscan accumulate within the casing and on the heat radiating coils betweenuses of the fan heater. When the heat radiating coils are activated, thetemperature of the outer surfaces of the coils can rise rapidly,particularly when the power output from the coils is relatively high, toa value in excess of 700° C. Consequently, some of the dust which hassettled on the coils between uses of the fan heater can be burnt,resulting in the emission of an unpleasant smell from the fan heater fora period of time.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a bladeless fanassembly for creating an air current, the fan assembly comprising adevice for creating an air flow and a nozzle comprising an interiorpassage for receiving the air flow and a mouth for emitting the airflow, the nozzle defining and extending about an opening through whichair from outside the fan assembly is drawn by the air flow emitted fromthe mouth, the fan assembly further comprising an air heater.

Through use of a bladeless fan assembly an air current can be generatedand a cooling effect created without the use of a bladed fan. Incomparison to a bladed fan assembly, the bladeless fan assembly leads toa reduction in both moving parts and complexity. Furthermore, withoutthe use of a bladed fan to project the air current from the fanassembly, a relatively uniform air current can be generated and guidedinto a room or towards a user. The heated air flow can travelefficiently out from the nozzle, losing less energy and velocity toturbulence than the air flow generated by prior art fan heaters. Anadvantage for a user is that the heated air flow can be experienced morerapidly at a distance of several meters from the fan assembly than whena prior art fan heater using a bladed fan is used to project the heatedair flow from the fan assembly.

The term ‘bladeless’ is used to describe a fan assembly in which airflow is emitted or projected forward from the fan assembly without theuse of moving blades. Consequently, a bladeless fan assembly can beconsidered to have an output area, or emission zone, absent movingblades from which the air flow is directed towards a user or into aroom. The output area of the bladeless fan assembly may be supplied witha primary air flow generated by one of a variety of different sources,such as pumps, generators, motors or other fluid transfer devices, andwhich may include a rotating device such as a motor rotor and/or abladed impeller for generating the air flow. The generated primary airflow can pass from the room space or other environment outside the fanassembly through the interior passage to the nozzle, and then back outto the room space through the mouth of the nozzle.

Hence, the description of a fan assembly as bladeless is not intended toextend to the description of the power source and components such asmotors that are required for secondary fan functions. Examples ofsecondary fan functions can include lighting, adjustment and oscillationof the fan assembly.

The direction in which air is emitted from the mouth is preferablysubstantially at a right angle to the direction in which the air flowpasses through at least part of the interior passage. Preferably, theair flow passes through at least part of the interior passage in asubstantially vertical plane, and the air is emitted from the mouth in asubstantially horizontal direction. The interior passage is preferablylocated towards the front of the nozzle, whereas the mouth is preferablylocated towards the rear of the nozzle and arranged to direct airtowards the front of the nozzle and through the opening. Consequently,the mouth is preferably shaped so as substantially to reverse the flowdirection of the air as it passes from the interior passage to an outletof the mouth. The mouth is preferably substantially U-shaped incross-section, and preferably narrows towards the outlet thereof.

The shape of the nozzle is not constrained by the requirement to includespace for a bladed fan. Preferably, the nozzle surrounds the opening.For example, the nozzle may extend about the opening by a distance inthe range from 50 to 250 cm. The nozzle may be an elongate, annularnozzle which preferably has a height in the range from 500 to 1000 mm,and a width in the range from 100 to 300 mm. Alternatively, the nozzlemay be a generally circular annular nozzle which preferably has a heightin the range from 50 to 400 mm. The interior passage is preferablyannular, and is preferably shaped to divide the air flow into two airstreams which flow in opposite directions around the opening.

The nozzle preferably comprises an inner casing section and an outercasing section which define the interior passage. Each section ispreferably formed from a respective annular member, but each section maybe provided by a plurality of members connected together or otherwiseassembled to form that section. The outer casing section is preferablyshaped so as to partially overlap the inner casing section to define atleast one outlet of the mouth between overlapping portions of theexternal surface of the inner casing section and the internal surface ofthe outer casing section of the nozzle. Each outlet is preferably in theform of a slot, preferably having a width in the range from 0.5 to 5 mm.The mouth may comprise a plurality of such outlets spaced about theopening. For example, one or more sealing members may be located withinthe mouth to define a plurality of spaced apart outlets. Such outletsare preferably of substantially the same size. Where the nozzle is inthe form of an elongate, annular nozzle, each outlet is preferablylocated along a respective elongate side of the inner periphery of thenozzle.

The nozzle may comprise a plurality of spacers for urging apart theoverlapping portions of the inner casing section and the outer casingsection of the nozzle. This can assist in maintaining a substantiallyuniform outlet width about the opening. The spacers are preferablyevenly spaced along the outlet.

The nozzle may comprise a plurality of stationary guide vanes locatedwithin the interior passage and each for directing a portion of the airflow towards the mouth. The use of such guide vanes can assist inproducing a substantially uniform distribution of the air flow throughthe mouth.

The nozzle may comprise a surface located adjacent the mouth and overwhich the mouth is arranged to direct the air flow emitted therefrom.Preferably, this surface is a curved surface, and more preferably is aCoanda surface. Preferably, the external surface of the inner casingsection of the nozzle is shaped to define the Coanda surface. A Coandasurface is a known type of surface over which fluid flow exiting anoutput orifice close to the surface exhibits the Coanda effect. Thefluid tends to flow over the surface closely, almost ‘clinging to’ or‘hugging’ the surface. The Coanda effect is already a proven, welldocumented method of entrainment in which a primary air flow is directedover a Coanda surface. A description of the features of a Coandasurface, and the effect of fluid flow over a Coanda surface, can befound in articles such as Reba, Scientific American, Volume 214, June1966 pages 84 to 92. Through use of a Coanda surface, an increasedamount of air from outside the fan assembly is drawn through the openingby the air emitted from the mouth.

In a preferred embodiment an air flow is created through the nozzle ofthe fan assembly. In the following description this air flow will bereferred to as the primary air flow. The primary air flow is emittedfrom the mouth of the nozzle and preferably passes over a Coandasurface. The primary air flow entrains air surrounding the mouth of thenozzle, which acts as an air amplifier to supply both the primary airflow and the entrained air to the user. The entrained air will bereferred to here as a secondary air flow. The secondary air flow isdrawn from the room space, region or external environment surroundingthe mouth of the nozzle and, by displacement, from other regions aroundthe fan assembly, and passes predominantly through the opening definedby the nozzle. The primary air flow directed over the Coanda surfacecombined with the entrained secondary air flow equates to a total airflow emitted or projected forward from the opening defined by thenozzle.

Preferably, the nozzle comprises a diffuser surface located downstreamof the Coanda surface. The diffuser surface directs the air flow emittedtowards a user's location while maintaining a smooth, even output,generating a suitable cooling effect without the user feeling a ‘choppy’flow. Preferably, the external surface of the inner casing section ofthe nozzle is shaped to define the diffuser surface.

Preferably the device for creating an air flow through the nozzlecomprises an impeller driven by a motor. This can provide a fan assemblywith efficient air flow generation. The means for creating an air flowpreferably comprises a DC brushless motor and a mixed flow impeller.This can avoid frictional losses and carbon debris from the brushes usedin a traditional brushed motor. Reducing carbon debris and emissions isadvantageous in a clean or pollutant sensitive environment such as ahospital or around those with allergies. While induction motors, whichare generally used in bladed fans, also have no brushes, a DC brushlessmotor can provide a much wider range of operating speeds than aninduction motor.

The heater may be arranged to heat the primary air flow upstream of themouth, with the secondary air flow being used to convey the heatedprimary air flow away from the fan assembly. Therefore, in a secondaspect the present invention provides a bladeless fan assembly forcreating an air current, the fan assembly comprising a device forcreating an air flow and a nozzle comprising an interior passage forreceiving the air flow and a mouth for emitting the air flow, the nozzledefining and extending about an opening through which air from outsidethe fan assembly is drawn by the air flow emitted from the mouth, thefan assembly further comprising a heater for heating the air flowupstream of the mouth.

Additionally, or alternatively, the heater may be arranged to heat thesecondary air flow. In one embodiment, at least part of the heater islocated downstream from the mouth to enable the heater to heat both theprimary air flow and the secondary air flow.

Preferably, the nozzle comprises the heater. At least part of the heatermay be located within the nozzle. The fan assembly may comprise aplurality of heaters arranged within the nozzle so as to extend aboutthe opening. Where the nozzle defines a circular opening, the heaterspreferably extend at least 270° about the opening and more preferably atleast 300° about the opening. Where the nozzle defines an elongateopening, the heaters are preferably located on at least the oppositeelongate sides of the opening.

In one embodiment the heater is arranged within the interior passage toheat the primary air flow upstream of the mouth. The heater may beconnected to one of the internal surface of the inner casing section andthe internal surface of the outer casing section so that at least partof the primary air flow passes over the heater before being emitted fromthe mouth. For example, the heater may comprise a plurality of thin-filmheaters connected to one, or both, of these internal surfaces.

Alternatively, the heater may be located between the internal surfacesso that substantially all of the primary air flow passes through theheater before being emitted from the mouth. For example, the heater maycomprise a porous heater located within the interior passage so that theprimary air flow passes through pores in the heater before being emittedfrom the mouth. The porous heater may be formed from ceramic material,preferably a PTC (positive temperature coefficient) ceramic heater whichis capable of rapidly heating the air flow upon activation. The heateris preferably configured to prevent the temperature of the heater fromrising above 200° C. so that no “burnt dust” odours are emitted from thefan assembly.

The ceramic material may be optionally coated in metallic or otherelectrically conductive material to facilitate connection of the heaterto a controller within the fan assembly for activating the heater.Alternatively, at least one non-porous heater may be mounted within ametallic frame located within the interior passage and which isconnected to the controller. The metallic frame serves to provide agreater surface area and hence better heat transfer, while alsoproviding a means of electrical connection to the heater.

The inner casing section and the outer casing section of the nozzle maybe formed from plastics material or other material having a relativelylow thermal conductivity (less than 1 Wm⁻¹K⁻¹), to prevent the externalsurfaces of the nozzle from becoming excessively hot during use of thefan assembly. However, the inner casing section may be formed frommaterial having a higher thermal conductivity than the outer casingsection so that the inner casing section becomes heated by the heater.This can allow heat to be transferred from the internal surface of theinner casing section—located upstream of the mouth—to the primary airflow passing through the interior passage, and from the external surfaceof the inner casing section—located downstream of the mouth—to theprimary and secondary air flows passing through the opening.

As an alternative to locating the heater within at least part of thenozzle, at least part of the heater may be located within a casinghousing the device for creating an air flow, or within another part ofthe fan assembly through which the air flow passes. Therefore, in athird aspect the present invention provides a bladeless fan assembly forcreating an air current, the fan assembly comprising a device forcreating an air flow and a nozzle comprising an interior passage forreceiving the air flow and a mouth for emitting the air flow, the nozzledefining and extending about an opening through which air from outsidethe fan assembly is drawn by the air flow emitted from the mouth, thefan assembly further comprising a porous heater through which the airflow passes.

As another example, the fan assembly may comprise a plurality of heaterslocated within the interior passage, and a plurality of heat radiatingfins connected to the heaters and extending at least partially acrossthe interior passage to transfer heat to the primary air flow. Two setsof such fins may be connected to each heater, with each set of finsextending from the heater towards a respective one of the internalsurface of the inner casing section and the internal surface of theouter casing section of the nozzle.

Alternatively, the heater may be otherwise located within the nozzle soas to be in thermal contact with the interior passage to heat the airflow upstream from the mouth. For example, the heater may be locatedwithin the inner casing section of the nozzle, with at least theinternal surface of the inner casing section being formed from thermallyconductive material to convey heat from the heater to the primary airflow passing through the interior passage. For example, the inner casingsection may be formed from material having a thermal conductivitygreater than 10 Wm⁻¹K⁻¹, and preferably from a metallic material such asaluminium or an aluminium alloy.

The fan assembly may comprise a plurality of heaters located within theinner casing section of the housing. For example, the fan assembly maycomprise a plurality of cartridge heaters located between the internalsurface and the external surface of the inner casing section. Where thenozzle is in the form of an elongate, annular nozzle, at least oneheater may be located along each opposing elongate surface of thenozzle. For example, the fan assembly may comprise a plurality of setsof cartridge heaters, with each set of cartridge heaters being locatedalong a respective side of the nozzle. Each set of cartridge heaters maycomprise two or more cartridge heaters.

The heaters may be located between an inner portion and an outer portionof the inner casing section of the nozzle. At least the outer portion ofthe inner casing section of the nozzle, and preferably both the innerportion and the outer portion of the inner casing section of the nozzle,is preferably formed from material having a higher thermal conductivitythan the outer casing section of the nozzle (preferably greater than 10Wm⁻¹K⁻¹), and preferably from a metallic material such as aluminium oran aluminium alloy. The use of a material such as aluminium can assistin reducing the thermal load of the heating means, and thereby increaseboth the rate at which the temperature of the heating means increasesupon activation and the rate at which the air is heated.

Such a portion of the inner casing section may be considered to formpart of the heater. Consequently, the heater may partially define theinterior passage of the nozzle. The heater may comprise one or both ofthe Coanda surface and the diffuser surface.

The heaters may be selectively activated by the user, eitherindividually or in pre-defined combinations, to vary the temperature ofthe air current emitted from the nozzle.

The heater may protrude at least partially across the opening. In oneembodiment, the heater comprises a plurality of heat radiating finsextending at least partially across the opening. This can assist inincreasing the rate at which heat is transferred from the heater to theair passing through the opening. Where the nozzle is in the form of anelongate, annular nozzle, a stack of heat radiating fins may be locatedalong each of the opposing elongate surfaces of the nozzle. Any dust orother detritus which may have settled on the upper surfaces of the heatradiating fins between successive uses of the fan assembly can berapidly blown from those surfaces by the air flow drawn through theopening when the fan assembly is switched on. During use, an externalsurface temperature of the heater is preferably in the range from 40 to70° C., preferably no more than around 50° C., so that user injury fromaccidental contact with the heat radiating fins or other externalsurface of the heater, and the “burning” of any dust remaining on theexternal surfaces of the heater, can be avoided.

The fan assembly may be desk or floor standing, or wall or ceilingmountable.

In a fourth aspect the present invention provides a fan heatercomprising a mouth for emitting an air flow, the mouth extending aboutan opening through which air from outside the fan heater is drawn by theair flow emitted from the mouth, and a Coanda surface over which themouth is arranged to direct the air flow, the fan heater furthercomprising an air heater.

In a fifth aspect the present invention provides a nozzle for a fanassembly for creating an air current, the nozzle comprising an interiorpassage for receiving an air flow and a mouth for emitting the air flow,the nozzle defining and extending about an opening through which airfrom outside the nozzle is drawn by the air flow emitted from the mouth,the nozzle further comprising an air heater.

In a sixth aspect the present invention provides a fan assemblycomprising a nozzle as aforementioned.

Features of the first aspect of the invention are equally applicable toany of the second to sixth aspects of the invention, and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only,with reference to the accompanying drawings, in which:

FIG. 1 is a front view of a domestic fan;

FIG. 2 is a perspective view of the fan of FIG. 1;

FIG. 3 is a cross-sectional view of the base of the fan of FIG. 1;

FIG. 4 is an exploded view of the nozzle of the fan of FIG. 1;

FIG. 5 is an enlarged view of area A indicated in FIG. 4;

FIG. 6 is a front view of the nozzle of FIG. 4;

FIG. 7 is a sectional view of the nozzle taken along line E-E in FIG. 6;

FIG. 8 is a sectional view of the nozzle taken along line D-D in FIG. 6;

FIG. 9 is an enlarged view of a section of the nozzle illustrated inFIG. 8;

FIG. 10 is a sectional view of the nozzle taken along line C-C in FIG.6;

FIG. 11 is an enlarged view of a section of the nozzle illustrated inFIG. 10;

FIG. 12 is a sectional view of the nozzle taken along line B-B in FIG.6;

FIG. 13 is an enlarged view of a section of the nozzle illustrated inFIG. 12;

FIG. 14 illustrates the air flow through part of the nozzle of the fanof FIG. 1;

FIG. 15 is a front view of a first alternative nozzle for the fan ofFIG. 1;

FIG. 16 is a perspective view of the nozzle of FIG. 15;

FIG. 17 is a sectional view of the nozzle of FIG. 15 taken along lineA-A in FIG. 15;

FIG. 18 is a sectional view of the nozzle of FIG. 15 taken along lineB-B in FIG. 15;

FIG. 19 is a perspective view of another domestic fan;

FIG. 20 is a front view of the fan of FIG. 19;

FIG. 21 is a side view of the nozzle of the fan of FIG. 19;

FIG. 22 is a sectional view taken along line A-A in FIG. 20; and

FIG. 23 is a sectional view taken along line B-B in FIG. 21.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 illustrate an example of a bladeless fan assembly. In thisexample, the bladeless fan assembly is in the form of a domestic towerfan 10 comprising a base 12 and a nozzle 14 mounted on and supported bythe base 12. The base 12 comprises a substantially cylindrical outercasing 16 mounted optionally on a disc-shaped base plate 18. The outercasing 16 comprises a plurality of air inlets 20 in the form ofapertures formed in the outer casing 16 and through which a primary airflow is drawn into the base 12 from the external environment. The base12 further comprises a plurality of user-operable buttons 21 and auser-operable dial 22 for controlling the operation of the fan 10. Inthis example the base 12 has a height in the range from 200 to 300 mm,and the outer casing 16 has a diameter in the range from 100 to 200 mm.

The nozzle 14 has an elongate, annular shape and defines a centralelongate opening 24. The nozzle 14 has a height in the range from 500 to1000 mm, and a width in the range from 150 to 400 mm. In this example,the height of the nozzle is around 750 mm and the width of the nozzle isaround 190 mm. The nozzle 14 comprises a mouth 26 located towards therear of the fan 10 for emitting air from the fan 10 and through theopening 24. The mouth 26 extends at least partially about the opening24. The inner periphery of the nozzle 14 comprises a Coanda surface 28located adjacent the mouth 26 and over which the mouth 26 directs theair emitted from the fan 10, a diffuser surface 30 located downstream ofthe Coanda surface 28 and a guide surface 32 located downstream of thediffuser surface 30. The diffuser surface 30 is arranged to taper awayfrom the central axis X of the opening 24 in such a way so as to assistthe flow of air emitted from the fan 10. The angle subtended between thediffuser surface 30 and the central axis X of the opening 24 is in therange from 5 to 15°, and in this example is around 7°. The guide surface32 is arranged at an angle to the diffuser surface 30 to further assistthe efficient delivery of a cooling air flow from the fan 10. The guidesurface 32 is preferably arranged substantially parallel to the centralaxis X of the opening 24 to present a substantially flat andsubstantially smooth face to the air flow emitted from the mouth 26. Avisually appealing tapered surface 34 is located downstream from theguide surface 32, terminating at a tip surface 36 lying substantiallyperpendicular to the central axis X of the opening 24. The anglesubtended between the tapered surface 34 and the central axis X of theopening 24 is preferably around 45°. The overall depth of the nozzle 24in a direction extending along the central axis X of the opening 24 isin the range from 100 to 150 mm, and in this example is around 110 mm.

FIG. 3 illustrates a sectional view through the base 12 of the fan 10.The outer casing 16 of the base 12 comprises a lower casing section 40and a main casing section 42 mounted on the lower casing section 40. Thelower casing section 40 houses a controller, indicated generally at 44,for controlling the operation of the fan 10 in response to depression ofthe user operable buttons 21 shown in FIGS. 1 and 2, and/or manipulationof the user operable dial 22. The lower casing section 40 may optionallycomprise a sensor 46 for receiving control signals from a remote control(not shown), and for conveying these control signals to the controller44. These control signals are preferably infrared or RF signals. Thesensor 46 is located behind a window 47 through which the controlsignals enter the lower casing section 40 of the outer casing 16 of thebase 12. A light emitting diode (not shown) may be provided forindicating whether the fan 10 is in a stand-by mode. The lower casingsection 40 also houses a mechanism, indicated generally at 48, foroscillating the main casing section 42 relative to the lower casingsection 40. The range of each oscillation cycle of the main casingsection 42 relative to the lower casing section 40 is preferably between60° and 120°, and in this example is around 90°. In this example, theoscillating mechanism 48 is arranged to perform around 3 to 5oscillation cycles per minute. A mains power cable 50 extends through anaperture formed in the lower casing section 40 for supplying electricalpower to the fan 10.

The main casing section 42 comprises a cylindrical grille 60 in which anarray of apertures 62 is formed to provide the air inlets 20 of theouter casing 16 of the base 12. The main casing section 42 houses animpeller 64 for drawing the primary air flow through the apertures 62and into the base 12. Preferably, the impeller 64 is in the form of amixed flow impeller. The impeller 64 is connected to a rotary shaft 66extending outwardly from a motor 68. In this example, the motor 68 is aDC brushless motor having a speed which is variable by the controller 44in response to user manipulation of the dial 22 and/or a signal receivedfrom the remote control. The maximum speed of the motor 68 is preferablyin the range from 5,000 to 10,000 rpm. The motor 68 is housed within amotor bucket comprising an upper portion 70 connected to a lower portion72. The upper portion 70 of the motor bucket comprises a diffuser 74 inthe form of a stationary disc having spiral blades. The motor bucket islocated within, and mounted on, a generally frusto-conical impellerhousing 76 connected to the main casing section 42. The impeller 42 andthe impeller housing 76 are shaped so that the impeller 64 is in closeproximity to, but does not contact, the inner surface of the impellerhousing 76. A substantially annular inlet member 78 is connected to thebottom of the impeller housing 76 for guiding the primary air flow intothe impeller housing 76.

A profiled upper casing section 80 is connected to the open upper end ofthe main casing section 42 of the base 12, for example by means ofsnap-fit connections. An O-ring sealing member may be used to form anair-tight seal between the main casing section 42 and the upper casingsection 80 of the base 12. The upper casing section 80 comprises achamber 86 for receiving the primary air flow from the main casingsection 42, and an aperture 88 through which the primary air flow passesfrom the base 12 into the nozzle 14.

Preferably, the base 12 further comprises silencing foam for reducingnoise emissions from the base 12. In this embodiment, the main casingsection 42 of the base 12 comprises a first, generally cylindrical foammember 89 a located beneath the grille 60, and a second, substantiallyannular foam member 89 b located between the impeller housing 76 and theinlet member 78.

The nozzle 14 will now be described with reference to FIGS. 4 to 13. Thenozzle 14 comprises an elongate, annular outer casing section 90connected to and extending about an elongate, annular inner casingsection 92. The inner casing section 92 defines the central opening 24of the nozzle 14, and has an external peripheral surface 93 which isshaped to define the Coanda surface 28, diffuser surface 30, guidesurface 32 and tapered surface 34.

The outer casing section 90 and the inner casing section 92 togetherdefine an annular interior passage 94 of the nozzle 14. The interiorpassage 94 is located towards the front of the fan 10. The interiorpassage 94 extends about the opening 24, and thus comprises twosubstantially vertically extending sections each adjacent a respectiveelongate side of the central opening 24, an upper curved section joiningthe upper ends of the vertically extending sections, and a lower curvedsection joining the lower ends of the vertically extending sections. Theinterior passage 94 is bounded by the internal peripheral surface 96 ofthe outer casing section 90 and the internal peripheral surface 98 ofthe inner casing section 92. The outer casing section 90 comprises abase 100 which is connected to, and over, the upper casing section 80 ofthe base 12, for example by a snap-fit connection. The base 100 of theouter casing section 90 comprises an aperture 102 which is aligned withthe aperture 88 of the upper casing section 80 of the base 12 andthrough which the primary air flow enters the lower curved portion ofthe interior passage 94 of the nozzle 14 from the base 12 of the fan 10.

With particular reference to FIGS. 8 and 9, the mouth 26 of the nozzle14 is located towards the rear of the fan 10. The mouth 26 is defined byoverlapping, or facing, portions 104, 106 of the internal peripheralsurface 96 of the outer casing section 90 and the external peripheralsurface 93 of the inner casing section 92, respectively. In thisexample, the mouth 26 comprises two sections each extending along arespective elongate side of the central opening 24 of the nozzle 14, andin fluid communication with a respective vertically extending section ofthe interior passage 94 of the nozzle 14. The air flow through eachsection of the mouth 26 is substantially orthogonal to the air flowthrough the respective vertically extending portion of the interiorpassage 94 of the nozzle 14. Each section of the mouth 26 issubstantially U-shaped in cross-section, and so as a result thedirection of the air flow is substantially reversed as the air flowpasses through the mouth 26. In this example, the overlapping portions104, 106 of the internal peripheral surface 96 of the outer casingsection 90 and the external peripheral surface 93 of the inner casingsection 92 are shaped so that each section of the mouth 26 comprises atapering portion 108 narrowing to an outlet 110. Each outlet 110 is inthe form of a substantially vertically extending slot, preferably havinga relatively constant width in the range from 0.5 to 5 mm. In thisexample each outlet 110 has a width of around 1.1 mm.

The mouth 26 may thus be considered to comprise two outlets 110 eachlocated on a respective side of the central opening 24. Returning toFIG. 4, the nozzle 14 further comprises two curved seal members 112, 114each for forming a seal between the outer casing section 90 and theinner casing section 92 so that there is substantially no leakage of airfrom the curved sections of the interior passage 94 of the nozzle 14.

In order to direct the primary air flow into the mouth 26, the nozzle 14comprises a plurality of stationary guide vanes 120 located within theinterior passage 94 and each for directing a portion of the air flowtowards the mouth 26. The guide vanes 120 are illustrated in FIGS. 4, 5,7, 10 and 11. The guide vanes 120 are preferably integral with theinternal peripheral surface 98 of the inner casing section 92 of thenozzle 14. The guide vanes 120 are curved so that there is nosignificant loss in the velocity of the air flow as it is directed intothe mouth 26. In this example the nozzle 14 comprises two sets of guidevanes 120, with each set of guide vanes 120 directing air passing alonga respective vertically extending portion of the interior passage 94towards its associated section of the mouth 26. Within each set, theguide vanes 120 are substantially vertically aligned and evenly spacedapart to define a plurality of passageways 122 between the guide vanes120 and through which air is directed into the mouth 26. The evenspacing of the guide vanes 120 provides a substantially evendistribution of the air stream along the length of the section of themouth 26.

With reference to FIG. 11, the guide vanes 120 are preferably shaped sothat a portion 124 of each guide vane 120 engages the internalperipheral surface 96 of the outer casing section 90 of the nozzle 24 soas to urge apart the overlapping portions 104, 106 of the internalperipheral surface 96 of the outer casing section 90 and the externalperipheral surface 93 of the inner casing section 92. This can assist inmaintaining the width of each outlet 110 at a substantially constantlevel along the length of each section of the mouth 26. With referenceto FIGS. 7, 12 and 13, in this example additional spacers 126 areprovided along the length of each section of the mouth 26, also forurging apart the overlapping portions 104, 106 of the internalperipheral surface 96 of the outer casing section 90 and the externalperipheral surface 93 of the inner casing section 92, to maintain thewidth of the outlet 110 at the desired level. Each spacer 126 is locatedsubstantially midway between two adjacent guide vanes 120. To facilitatemanufacture the spacers 126 are preferably integral with the externalperipheral surface 98 of the inner casing section 92 of the nozzle 14.Additional spacers 126 may be provided between adjacent guide vanes 120if so desired.

In use, when the user depresses an appropriate one of the buttons 21 onthe base 12 of the fan 10 the controller 44 activates the motor 68 torotate the impeller 64, which causes a primary air flow to be drawn intothe base 12 of the fan 10 through the air inlets 20. The primary airflow may be up to 30 liters per second, more preferably up to 50 litersper second. The primary air flow passes through the impeller housing 76and the upper casing section 80 of the base 12, and enters the base 100of the outer casing section 90 of the nozzle 14, from which the primaryair flow enters the interior passage 94 of the nozzle 14.

With reference also to FIG. 14 the primary air flow, indicated at 148,is divided into two air streams, one of which is indicated at 150 inFIG. 14, which pass in opposite directions around the central opening 24of the nozzle 14. Each air stream 150 enters a respective one of the twovertically extending sections of the interior passage 94 of the nozzle14, and is conveyed in a substantially vertical direction up througheach of these sections of the interior passage 94. The set of guidevanes 120 located within each of these sections of the interior passage94 directs the air stream 150 towards the section of the mouth 26located adjacent that vertically extending section of the interiorpassage 94. Each of the guide vanes 120 directs a respective portion 152of the air stream 150 towards the section of the mouth 26 so that thereis a substantially uniform distribution of the air stream 150 along thelength of the section of the mouth 26. The guide vanes 120 are shaped sothat each portion 152 of the air stream 150 enters the mouth 26 in asubstantially horizontal direction. Within each section of the mouth 26,the flow direction of the portion of the air stream is substantiallyreversed, as indicated at 154 in FIG. 14. The portion of the air streamis constricted as the section of the mouth 26 tapers towards the outlet110 thereof, channeled around the spacer 126 and emitted through theoutlet 110, again in a substantially horizontal direction.

The primary air flow emitted from the mouth 26 is directed over theCoanda surface 28 of the nozzle 14, causing a secondary air flow to begenerated by the entrainment of air from the external environment,specifically from the region around the outlets 110 of the mouth 26 andfrom around the rear of the nozzle 14. This secondary air flow passesthrough the central opening 24 of the nozzle 14, where it combines withthe primary air flow to produce a total air flow 156, or air current,projected forward from the nozzle 14.

The even distribution of the primary air flow along the mouth 26 of thenozzle 14 ensures that the air flow passes evenly over the diffusersurface 30. The diffuser surface 30 causes the mean speed of the airflow to be reduced by moving the air flow through a region of controlledexpansion. The relatively shallow angle of the diffuser surface 30 tothe central axis X of the opening 24 allows the expansion of the airflow to occur gradually. A harsh or rapid divergence would otherwisecause the air flow to become disrupted, generating vortices in theexpansion region. Such vortices can lead to an increase in turbulenceand associated noise in the air flow, which can be undesirable,particularly in a domestic product such as a fan. In the absence of theguide vanes 120 most of the primary air flow would tend to leave the fan10 through the upper part of the mouth 26, and to leave the mouth 26upwardly at an acute angle to the central axis of the opening 24. As aresult there would be an uneven distribution of air within the aircurrent generated by the fan 10. Furthermore, most of the air flow fromthe fan 10 would not be properly diffused by the diffuser surface 30,leading to the generation of an air current with much greaterturbulence.

The air flow projected forwards beyond the diffuser surface 30 can tendto continue to diverge. The presence of the guide surface 32 extendingsubstantially parallel to the central axis X of the opening 30 tends tofocus the air flow towards the user or into a room.

An alternative nozzle 200 which may be mounted on and supported by thebase 12 in place of the nozzle 14 will now be described with referenceto FIGS. 15 to 18. The nozzle 200 is used to convert the fan 10 into afan heater which may be used to create either a cooling air currentsimilar to the fan 10 or a warming air current as required by the user.The nozzle 200 has substantially the same size and shape as the nozzle14, and so defines a central elongate opening 202. As with the nozzle14, the nozzle 200 comprises a mouth 204 located towards the rear of thenozzle 200 for emitting air through the opening 202. The mouth 204extends at least partially about the opening 202. The inner periphery ofthe nozzle 200 comprises a Coanda surface 206 located adjacent the mouth204 and over which the mouth 204 directs the air emitted from the nozzle200, and a diffuser surface 208 located downstream of the Coanda surface206. The diffuser surface 208 is arranged to taper away from the centralaxis X of the opening 202 in such a way so as to assist the flow of airemitted from the fan heater. The angle subtended between the diffusersurface 208 and the central axis X of the opening 24 is in the rangefrom 5 to 25°, and in this example is around 7°. The diffuser surface208 terminates at a front surface 210 lying substantially perpendicularto the central axis X of the opening 202.

Similar to the nozzle 14, the nozzle 200 comprises an elongate, annularouter casing section 220 connected to and extending about an elongate,annular inner casing section 222. The outer casing section 220 issubstantially the same as the outer casing section 90 of the nozzle 14.The outer casing section 220 is preferably formed from plasticsmaterial. The outer casing section 220 comprises a base 224 which isconnected to, and over, the upper casing section 80 of the base 12, forexample by a snap-fit connection. The inner casing section 222 definesthe central opening 202 of the nozzle 200, and has an externalperipheral surface 226 which is shaped to define the Coanda surface 206,diffuser surface 208, and end surface 210.

The outer casing section 220 and the inner casing section 222 togetherdefine an annular interior passage 228 of the nozzle 200. The interiorpassage 228 extends about the opening 202, and thus comprises twosubstantially vertically extending sections each adjacent a respectiveelongate side of the central opening 202, an upper curved sectionjoining the upper ends of the vertically extending sections, and a lowercurved section joining the lower ends of the vertically extendingsections. The interior passage 228 is bounded by the internal peripheralsurface 230 of the outer casing section 220 and the internal peripheralsurface 232 of the inner casing section 222. The base 224 of the outercasing section 220 comprises an aperture 234 which is aligned with theaperture 88 of the upper casing section 80 of the base 12 when thenozzle 200 is connected to the base 12. In use, the primary air flowpasses through the aperture 234 from the base 12, and enters the lowercurved portion of the interior passage 228 of the nozzle 220.

With particular reference to FIGS. 17 and 18, the mouth 204 of thenozzle 200 is substantially the same as the mouth 26 of the nozzle 14.The mouth 204 is located towards the rear of the nozzle 200, and isdefined by overlapping, or facing, portions of the internal peripheralsurface 230 of the outer casing section 220 and the external peripheralsurface 226 of the inner casing section 222, respectively. The mouth 204comprises two sections each extending along a respective elongate sideof the central opening 202 of the nozzle 200, and in fluid communicationwith a respective vertically extending section of the interior passage228 of the nozzle 200. The air flow through each section of the mouth204 is substantially orthogonal to the air flow through the respectivevertically extending portion of the interior passage 228 of the nozzle200. The mouth 204 is shaped so that the direction of the air flow issubstantially reversed as the air flow passes through the mouth 204. Theoverlapping portions of the internal peripheral surface 230 of the outercasing section 220 and the external peripheral surface 226 of the innercasing section 222 are shaped so that each section of the mouth 204comprises a tapering portion 236 narrowing to an outlet 238. Each outlet238 is in the form of a substantially vertically extending slot,preferably having a relatively constant width in the range from 0.5 to 5mm, more preferably in the range from 1 to 2 mm. In this example eachoutlet 238 has a width of around 1.7 mm. The mouth 204 may thus beconsidered to comprise two outlets 238 each located on a respective sideof the central opening 202.

In this example, the inner casing section 222 of the nozzle 200comprises a number of connected sections. The inner casing section 222comprises a lower section 240 which defines, with the outer casingsection 220, the lower curved section of the interior passage 228. Thelower section 240 of the inner casing section 222 of the nozzle 200 ispreferably formed from plastics material. The inner casing section 222also comprises an upper section 242 which defines, with the outer casingsection 220, the upper curved section of the interior passage 228. Theupper section 242 of the inner casing section 222 is substantiallyidentical to the lower section 240 of the inner casing section 222. Asindicated in FIG. 18, each of the lower section 240 and the uppersection 242 of the inner casing section 222 forms a seal with the outercasing section 220 so that there is substantially no leakage of air fromthe curved sections of the interior passage 228 of the nozzle 200.

The inner casing section 222 of the nozzle 200 further comprises two,substantially vertically extending sections each extending along arespective side of the central opening 202 and between the lower section240 and the upper section 242 of the inner casing section 222. Eachvertically extending section of the inner casing section 222 comprisesan inner plate 244 and an outer plate 246 connected to the inner plate244. Each of the inner plate 244 and the outer plate 246 is preferablyformed from material having a higher thermal conductivity than the outercasing section 220 of the nozzle 200, and in this example each of theinner plate 244 and the outer plate 246 is formed from aluminium or analuminium alloy. The inner plates 244 define, with the outer casingsection 220, the vertically extending sections of the interior passage228 of the nozzle 200. The outer plates 246 define the Coanda surface206 over which air emitted from the mouth 204 is directed, and an endportion 208 b of the diffuser surface 208.

Each vertically extending section of the inner casing portion 222comprises a set of cartridge heaters 248 located between the inner plate244 and the outer plate 246 thereof. In this embodiment, each set ofcartridge heaters 248 comprises two, substantially vertically extendingcartridge heaters 248, each having a length which is substantially thesame as the lengths of the inner plate 244 and the outer plate 246. Eachcartridge heater 248 may be connected to the controller 44 by powerleads (not shown) extending through the base 234 of the outer casingportion 220 of the nozzle 200. The leads may terminate in connectorswhich mate with co-operating connectors located on the upper casingsection 80 of the base 12 when the nozzle 200 is connected to the base12. These co-operating connectors may be connected to power leadsextending within the base 12 to the controller 44. At least oneadditional user operable button or dial may be provided on the lowercasing section 40 of the base 12 to enable a user to activateselectively each set of cartridge heaters 248.

Each vertically extending section of the inner casing portion 222further comprises a heat sink 250 connected to the outer plate 246 bypins 252. In this example, each heat sink 250 comprises an upper portion250 a and a lower portion 250 b each connected to the outer plate 246 byfour pins 252. Each portion of the heat sink 250 comprises a verticallyextending heat sink plate 254 located within a recessed portion of theouter plate 246 so that the external surface of the heat sink plate 254is substantially flush with the external surface of the outer plate 246.The external surface of the heat sink plate 254 forms part of thediffuser surface 208. The heat sink plate 254 is preferably formed fromthe same material as the outer plate 246. Each portion of the heat sink250 comprises a stack of heat radiating fins 256 for dissipating heat tothe air flow passing through the opening 202. Each heat radiating fin256 extends outwardly from the heat sink plate 254 and partially acrossthe opening 202. With reference to FIG. 17, in this example each heatradiating fin 256 is substantially trapezoidal. The heat radiating fins256 are preferably formed from the same material as the heat sink plate254, and are preferably integral therewith.

Each vertically extending section of the inner casing section 222 of thenozzle 200 may thus be considered as a respective heating unit forheating the air flow passing through the opening 202, with each of theseheating units comprising an inner plate 244, an outer plate 246, a setof cartridge heaters 248 and a heat sink 250. Consequently, at leastpart of each heating unit is located downstream from the mouth 204, atleast part of each heating unit defines part of the interior passage 228with the outer casing portion 220 of the nozzle 200, and the interiorpassage 228 extends about these heating units.

The inner casing section 222 of the nozzle 200 may also comprise guidevanes located within the interior passage 228 and each for directing aportion of the air flow towards the mouth 204. The guide vanes arepreferably integral with the internal peripheral surfaces of the innerplates 244 of the inner casing section 222 of the nozzle 200. Otherwise,these guide vanes are preferably substantially the same as the guidevanes 120 of the nozzle 14 and so will not be described in detail here.Similar to the nozzle 14, spacers may be provided along the length ofeach section of the mouth 204 for urging apart the overlapping portionsof the internal peripheral surface 230 of the outer casing section 220and the external peripheral surface 226 of the inner casing section 222to maintain the width of the outlets 238 at the desired level.

In use, an air current of relatively low turbulence is created andemitted from the fan heater in the same way that such an air current iscreated and emitted from the fan 10, as described above with referenceto FIGS. 1 to 14. When none of the heating units have been activated bythe user, the cooling effect of the fan heater is similar to that of thefan 10. When the user has depressed the additional button on the base12, or manipulated the additional dial, to activate one or more of theheater units, the controller 44 activates the set of cartridge heaters248 of those heater units. The heat generated by the cartridge heaters248 is transferred by conduction to the inner plate 244, the outer plate246, and the heat sink 250 associated with each activated set ofcartridge heaters 248. The heat is dissipated from the external surfacesof the heat radiating fins 256 to the air flow passing through theopening 202, and, to a much lesser extent, from the internal surface ofthe inner plate 244 to part of the primary air flow passing through theinterior passage 228. Consequently, a current of warm air is emittedfrom the fan heater. This current of warm air can travel efficiently outfrom the nozzle 200, losing less energy and velocity to turbulence thanthe air flow generated by prior art fan heaters.

Due to the relatively high flow rate of the air current generated by thefan heater, the temperature of the external surfaces of the heatingunits can be maintained at a relatively low temperature, for example inthe range of 50 to 70° C., while enabling a user located several metersfrom the fan heater to experience rapidly the heating effect of the fanheater. This can inhibit serious user injury through accidental contactwith the external surfaces of the heating units during use of the fanheater. Another advantage associated with this relatively lowtemperature of the external surfaces of the heating units is that thistemperature is insufficient to generate an unpleasant “burnt dust” smellwhen the heating unit is activated.

FIGS. 19 to 21 illustrate another alternative nozzle 300 mounted on andsupported by the base 12 in place of the nozzle 14. Similar to thenozzle 200, the nozzle 300 is used to convert the fan 10 into a fanheater which may be used to create either a cooling air current similarto the fan 10 or a warming air current as required by the user. Thenozzle 300 has a different size and shape to the nozzle 14 and thenozzle 200. In this example, the nozzle 300 defines a circular, ratherthan an elongate, central opening 302. The nozzle 300 preferably has aheight in the range from 150 to 400 mm, and in this example has a heightof around 200 mm.

As with the previous nozzles 14, 200, the nozzle 300 comprises a mouth304 located towards the rear of the nozzle 300 for emitting the primaryair flow through the opening 302. In this example, the mouth 304 extendssubstantially completely about the opening 302. The inner periphery ofthe nozzle 300 comprises a Coanda surface 306 located adjacent the mouth304 and over which the mouth 304 directs the air emitted from the nozzle300, and a diffuser surface 308 located downstream of the Coanda surface306. In this example, the diffuser surface 308 is a substantiallycylindrical surface co-axial with the central axis X of the opening 302.A visually appealing tapered surface 310 is located downstream from thediffuser surface 308, terminating at a tip surface 312 lyingsubstantially perpendicular to the central axis X of the opening 302.The angle subtended between the tapered surface 310 and the central axisX of the opening 302 is preferably around 45°. The overall depth of thenozzle 300 in a direction extending along the central axis X of theopening 302 is preferably in the range from 90 to 150 mm, and in thisexample is around 100 mm.

FIG. 22 illustrates a top sectional view through the nozzle 300. Similarto the nozzles 14, 200, the nozzle 300 comprises an annular outer casingsection 314 connected to and extending about an annular inner casingsection 316. The casing sections 314, 316 are preferably connectedtogether at or around the tip 312 of the nozzle 300. Each of thesesections may be formed from a plurality of connected parts, but in thisexample each of the outer casing section 314 and the inner casingsection 316 is formed from a respective, single moulded part. The innercasing section 316 defines the central opening 302 of the nozzle 300,and has an external peripheral surface 318 which is shaped to define theCoanda surface 306, diffuser surface 308, and tapered surface 310. Eachof the casing sections 314, 316 is preferably formed from plasticsmaterial.

The outer casing section 314 and the inner casing section 316 togetherdefine an annular interior passage 320 of the nozzle 300. Thus, theinterior passage 320 extends about the opening 24. The interior passage320 is bounded by the internal peripheral surface 322 of the outercasing section 314 and the internal peripheral surface 324 of the innercasing section 316. The outer casing section 314 comprises a base 326which is connected to, and over, the open upper end of the main body 42of the base 12, for example by a snap-fit connection. Similar to thebase 100 of the outer casing section 90 of the nozzle 14, the base 326of the outer casing section 314 comprises an aperture through which theprimary air flow enters the interior passage 320 of the nozzle 14 fromthe open upper end of the main body 42 of the base 12.

The mouth 304 is located towards the rear of the nozzle 300. Similar tothe mouth 26 of the nozzle 14, the mouth 304 is defined by overlapping,or facing, portions of the internal peripheral surface 322 of the outercasing section 314 and the external peripheral surface 318 of the innercasing section 316. In this example, the mouth 304 is substantiallyannular and, as illustrated in FIG. 21, has a substantially U-shapedcross-section when sectioned along a line passing diametrically throughthe nozzle 14. In this example, the overlapping portions of the internalperipheral surface 322 of the outer casing section 314 and the externalperipheral surface 318 of the inner casing section 316 are shaped sothat the mouth 302 tapers towards an outlet 328 arranged to direct theprimary air flow over the Coanda surface 306. The outlet 328 is in theform of an annular slot, preferably having a relatively constant widthin the range from 0.5 to 5 mm. In this example the outlet 328 has awidth of around 1 to 2 mm. Spacers may be spaced about the mouth 302 forurging apart the overlapping portions of the internal peripheral surface322 of the outer casing section 314 and the external peripheral surface318 of the inner casing section 316 to maintain the width of the outlet328 at the desired level. These spacers may be integral with either theinternal peripheral surface 322 of the outer casing section 314 or theexternal peripheral surface 318 of the inner casing section 316.

The nozzle 300 comprises at least one heater for heating the primary airflow before it is emitted from the mouth 304. In this example, thenozzle 300 comprises a plurality of heaters, indicated generally at 330,located within the interior passage 320 of the nozzle 300 and throughwhich the primary air flow passes as it flows through the nozzle 300. Asillustrated in FIG. 23, the heaters 330 are preferably arranged in anarray which extends about the opening 302, and is preferably located ina plane extending orthogonal to the axis X of the nozzle 300. The arraypreferably extends at least 270° about the axis X, more preferably atleast 315° about the axis X. In this example, the array of heaters 330extends around 320° about the axis, with each end of the arrayterminating at or around a respective side of the aperture in the base326 of the outer casing section 314. The array of heaters 330 ispreferably arranged towards the rear of the interior passage 320 so thatsubstantially all of the primary air flow passes through the array ofheaters 330 before entering the mouth 304, and less heat is lost to theplastic parts of the nozzle 300.

The array of heaters 330 may be provided by a plurality of ceramicheaters arranged side-by-side within the interior passage 320. Theheaters 330 are preferably formed from porous, positive temperaturecoefficient (PTC) ceramic material, and may be located within respectiveapertures formed in an arcuate metallic frame which is located within,for example, the outer casing section 314 before the inner casingsection 316 is attached thereto. Power leads extending from the framemay extend through the base 326 of the outer casing section 314 andterminate in connectors which mate with co-operating connectors locatedon the upper casing section 80 of the base 12 when the nozzle 300 isconnected to the base 12. These co-operating connectors may be connectedto power leads extending within the base 12 to the controller 44. Atleast one additional user operable button or dial may be provided on thelower casing section 40 of the base 12 to enable a user to activate thearray of heaters 330. During use the maximum temperature of the heaters330 is around 200° C.

In use, the operation of the fan assembly 10 with the nozzle 300 is muchthe same as the operation of the fan assembly with the nozzle 200. Whenthe user has depressed the additional button on the base 12, ormanipulated the additional dial, the controller 44 activates the arrayof heaters 330. The heat generated by the array of heaters 330 istransferred by convection to the primary air flow passing through theinterior passage 320 so that a heated primary air flow is emitted fromthe mouth 304 of the nozzle 300. The heated primary air flow entrainsair from the room space, region or external environment surrounding themouth 304 of the nozzle 300 as it passes over the Coanda surface 306 andthrough the opening 302 defined by the nozzle 300, resulting in anoverall air flow projected forward from the fan assembly 10 which has alower temperature than the primary air flow emitted from the mouth 304,but a higher temperature than the air entrained from the externalenvironment. Consequently, a current of warm air is emitted from the fanassembly. As with the current of warm air generated by the nozzle 200,this current of warm air can travel efficiently out from the nozzle 300,losing less energy and velocity to turbulence than the air flowgenerated by prior art fan heaters.

The invention is not limited to the detailed description given above.Variations will be apparent to the person skilled in the art.

The invention claimed is:
 1. A nozzle for a fan assembly for creating anair current, the nozzle comprising an interior passage for receiving anair flow and a mouth for emitting the air flow, the nozzle defining andextending about a central opening through which air from outside thenozzle is drawn by the air flow emitted from the mouth, the nozzlefurther comprising a plurality of heaters arranged in a rear of theinterior passage, relative to a flow direction of the air from outsidein the central opening, so that the air flow passes through theplurality of heaters before entering the mouth and arranged to extendabout the central opening, wherein the heaters can be selectivelyactivated.
 2. The nozzle of claim 1, wherein the heaters are activatedindividually.
 3. The nozzle of claim 1, wherein the heaters areactivated in pre-defined combinations.
 4. The nozzle of claim 1, whereinthe heaters extend about the opening by at least 270°.
 5. The nozzle ofclaim 1, wherein the heaters extend about the opening by at least 315°.6. The nozzle of claim 1, wherein the heaters comprise porous heaters.7. The nozzle of claim 1, wherein the heaters comprise a plurality ofheat radiating fins.
 8. The nozzle of claim 1, wherein the heaters arein thermal contact with the interior passage.
 9. The nozzle of claim 1,wherein the interior passage is annular.
 10. The nozzle of claim 1,comprising an inner casing section and an outer casing section whichtogether define the interior passage and the mouth.
 11. The nozzle ofclaim 10, wherein the heaters are arranged to heat the inner casingsection of the nozzle.
 12. The nozzle of claim 10, wherein the innercasing section of the nozzle comprises said heaters.
 13. The nozzle ofclaim 1, comprising a surface located adjacent the mouth and over whichthe mouth is arranged to direct the air flow.
 14. The nozzle of claim13, wherein the surface comprises a Coanda surface.
 15. The nozzle ofclaim 14, wherein the nozzle comprises a diffuser surface locateddownstream from the Coanda surface.